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Abstract:

The technology disclosed herein relates to a method for lead analysis for
an implanted medical device. A summary data record is retrieved
associated with one or more episodes from an implanted medical device
through a communication module. Episode selection criteria are applied to
the summary data record by a processing module. One or more episode data
records are retrieved from the implanted medical device for one or more
episodes for which the episode selection criteria was satisfied. Noise
detection criteria are applied to the episode data record. A notification
module is configured to generate an alert if the noise detection criteria
are satisfied

Claims:

1. An external device for determining a lead-related condition associated
with an implantable medical device (IMD) capable of being implanted in a
patient: (a) a communication module configured to retrieve patient data
from an IMD, wherein the patient data comprises at least episode data
records each associated with an episode and a summary data record
corresponding to one or more episodes; (b) a processing module configured
to execute rapid sensing analysis comprising: (i) initiate periodic
retrieval of a summary data record by the communication module from the
IMD; (ii) apply an episode selection criteria to the summary data record
to identify one or more episodes of interest, (iii) initiate retrieval
from the IMD by the communication module of one or more episode data
records associated with each episode of interest, and (iv) apply noise
detection criteria to the one or more episode data records; and (c) a
notification module configured to generate an alert if the noise
detection criteria are satisfied.

2. The device of claim 1 wherein each summary data record of the one or
more summary data records comprises a shock indicator indicating whether
a shock was delivered by the IMD for a particular episode and the episode
selection criteria excludes episodes during which a shock was delivered
by the IMD.

3. The device of claim 1 wherein the processing module is configured to
apply episode selection criteria to each summary data record comprising
whether the episode was sustained and whether a shock was delivered.

4. The device of claim 3, wherein the processing module is configured to
apply episode selection criteria to each summary data record comprising a
therapy indicator indicating whether no therapy was attempted and whether
anti-tachycardia pacing (ATP) was delivered by the IMD.

5. The device of claim 4, wherein the processing module is configured
such that the episode selection criteria are satisfied if ATP was
delivered during an episode.

6. The device of claim 3, wherein the processing module is configured
such that the episode selection criteria are satisfied if an episode was
sustained absent a delivered shock.

7. The device of claim 1 wherein the processing module is configured to
apply noise detection criteria comprising first noise sub-criteria and
second noise sub-criteria, and the noise detection criteria are satisfied
if either the first or second noise sub-criteria are satisfied.

8. The device of claim 7 wherein: the first noise sub-criteria are
satisfied if episodes with ATP delivered or episodes with a diverted
shock are determined to contain noise based on applying a noise
definition; and the second noise sub-criteria are satisfied if sustained
episodes with no therapy attempted on two different days within a first
time period are determined to contain noise based on applying the noise
definition.

9. The device of claim 8 wherein the noise definition is satisfied if
there are a threshold number of ventricular sensed beats that satisfy a
first fast interval threshold.

10. The device of claim 9 wherein the threshold number of ventricular
sensed beats is four.

11. The device of claim 1, wherein the processing module is further
configured to execute an impedance spike analysis comprising:
determination of an impedance median; identification of a number of
impedance spikes relative to the median; and notification if the number
of impedance spikes is more than a spike threshold.

12. The device of claim 11, further comprising a user interface to
optionally select each of impedance spike analysis and rapid sensing
analysis.

14. A method for lead analysis for an implanted medical device (IMD)
comprising: (a) retrieving a summary data record associated with one or
more episodes from an IMD through a communication module; (b) applying
episode selection criteria to the summary data record by a processing
module; (c) retrieving one or more episode data records from the IMD for
one or more episodes for which the episode selection criteria was
satisfied; (d) applying noise detection criteria to the episode data
record; and (e) generating an alert if the noise detection criteria are
satisfied.

15. The method of claim 14 wherein the summary data record includes a
shock indicator indicating whether a shock was delivered by the IMD and
wherein the episode selection criteria excludes episodes during which a
shock was delivered by the IMD.

16. The method of claim 14 wherein applying episode selection criteria to
the summary data record comprises determining whether the episode was
sustained, whether shock was delivered, and whether anti-tachycardia
pacing (ATP) was delivered by the IMD.

17. The method of claim 16, wherein the episode selection criteria are
satisfied if ATP was delivered during an episode.

18. The method of claim 16, wherein the episode selection criteria are
satisfied if an episode was sustained absent a delivered shock.

19. The method of claim 14, further comprising executing an impedance
spike analysis comprising: determining an impedance median; identifying a
number of impedance spikes relative to the median; and notifying if the
number of impedance spikes is more than a spike threshold.

20. An external device for determining a lead-related condition
associated with an implantable medical device (IMD) capable of being
implanted in a patient: (a) a communication module configured to retrieve
patient data from an IMD, wherein the patient data comprises at least one
or more episode data records each associated with an episode and a
summary data record; (b) a processing module configured to execute rapid
sensing analysis comprising: (i) initiate periodic retrieval of a summary
data record by the communication module from the IMD; (ii) apply an
episode selection criteria to the retrieved summary data record to
identify one or more episodes of interest, (iii) initiate retrieval from
the IMD by the communication module of one or more episode data records
associated with each episode of interest, and (iv) apply noise detection
criteria to the one or more episode data record or records; and (c) a
notification module configured to generate an alert if the noise
detection criteria are satisfied; wherein each summary data record
includes a shock indicator indicating whether a shock was delivered by
the IMD for a particular episode and the episode selection criteria
excludes episodes during which a shock was delivered by the IMD.

Description:

[0001] This application claims the benefit of U.S. Provisional Application
No. 61/734,198 filed Dec. 6, 2012, the content of which is herein
incorporated by reference in its entirety.

[0003] Implantable medical devices are commonly used to treat and monitor
patients with various medical conditions. Implanted medical devices used
in the treatment and monitoring of heart conditions, for example,
generally has a hermetically sealed housing that holds at least a power
source and processor, as well as one or more leads running from the
housing to locations in or about the heart. One or more electrodes along
each lead provide electrical sensing and/or stimulating functionality to
the heart from the housing.

[0004] Over time there can be wear and tear on a lead based on its
durability and its environment, which can cause functionality problems
such as inaccurate sensing, inaccurate treatment, and the like. As such,
it is desirable for caregivers to be able to accurately identify a
problematic lead with the information available, while minimizing "false
positive" identification of problematic leads.

SUMMARY OF THE INVENTION

[0005] The technology disclosed herein relates to an external device for
determining a lead-related condition associated with an implantable
medical device (IMD). The external device generally has a communication
module, a processing module, and a notification module. The communication
module is configured to retrieve patient data from an IMD, where "patient
data" includes at least episode data records and a summary data record.
Each episode data record is generally associated with an episode and the
summary data record corresponds to one or more episodes. The processing
module executes rapid sensing analysis. Rapid sensing analysis generally
includes the periodic retrieval of a summary data record from an IMD. The
retrieval can be executed by a communication module. Rapid sensing
applies episode selection criteria to the summary data record to identify
one or more episodes of interest, and retrieval is initiated from the IMD
of one or more episode data records associated with each episode of
interest. Noise detection criteria are applied to the one or more episode
data records. The notification module is configured to generate an alert
if the noise detection criteria are satisfied.

[0006] In other embodiment, a method for lead analysis for an implanted
medical device is described. A summary data record is retrieved
associated with one or more episodes from an implanted medical device
through a communication module. Episode selection criteria are applied to
the summary data record by a processing module. One or more episode data
records are retrieved from the implanted medical device for one or more
episodes for which the episode selection criteria was satisfied. Noise
detection criteria is applied to the episode data record. Another step is
generating an alert if the noise detection criteria are satisfied.

[0007] The technology disclosed herein also relates to an external device
for determining a lead-related condition associated with an implantable
medical device (IMD). The external device generally has a communication
module, a processing module, and a notification module. The communication
module is configured to retrieve patient data from an IMD, where "patient
data" includes at least episode data records and a summary data record.
Each episode data record is generally associated with an episode and the
summary data record corresponds to one or more episodes. Each summary
data record includes a shock indicator indicating whether a shock was
delivered by the IMD for a particular episode and the episode selection
criteria excludes episodes during which a shock was delivered by the IMD.
The processing module executes rapid sensing analysis. Rapid sensing
analysis generally includes the periodic retrieval of a summary data
record from an IMD. The retrieval can be executed by a communication
module. Rapid sensing applies episode selection criteria to the summary
data record to identify one or more episodes of interest, and retrieval
is initiated from the IMD of one or more episode data records associated
with each episode of interest. Noise detection criteria are applied to
the one or more episode data records. The notification module is
configured to generate an alert if the noise detection criteria are
satisfied.

[0016] FIG. 9 depicts a screenshot of an example implementation of the
technology disclosed herein.

[0017] FIG. 10 depicts an example cardiac rhythm management system
consistent with at least one implementation of the technology disclosed
herein.

[0018] FIG. 11 depicts a schematic of a patient management system
consistent with at least one implementation of the technology disclosed
herein.

[0019] FIG. 12 depicts a schematic of various components consistent with
some embodiments of the technology disclosed herein.

[0020] FIG. 13 depicts a schematic of some components of an exemplary
implantable medical device.

[0021] The invention may be more completely understood and appreciated in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings.

DETAILED DESCRIPTION

[0022] FIG. 1 depicts an example implementation of an implanted medical
device (IMD) 110, which is a cardiac rhythm management device. Examples
of IMDs 110 include, without limitation, a pacer, a defibrillator, a
cardiac resynchronization therapy (CRT) device, or a combination of such
devices. The system also typically includes an IMD programmer or other
external device 170 that communicates wireless signals 190 with the IMD
110, such as by using radio frequency (RF) or other telemetry signals. In
one embodiment, the external device 170 communicates with the IMD at
scheduled intervals to download information from the IMD. In one example,
the external device 170 communicates once every 24 hours with the IMD.
During a communication session, the IMD downloads information about the
patient and any therapy delivered during the time interval since the
previous communication session. The downloaded information can include a
summary of any episodes that occurred during the time interval or a
subset of those episodes. This summary information will be referred to
herein as a summary data record or episode summary data. The summary data
record and can include episode data records for specific episodes, such
as episodes where a shock was delivered. The summary data record can
include notification and alerts from the IMD along with many other types
of information. Examples of information in the summary data record will
be further described herein. Episode is defined to mean activity of a
patient's body within a time period of particular interest, which is
determined according to algorithms stored in the IMD. The time period can
be a time when there is abnormal activity, for example, abnormal cardiac
activity. One example of an episode of particular interest during lead
analysis is a tachy episode, where the IMD algorithms indicate that the
patient's heart is beating abnormally fast. The IMD 110 is coupled by one
or more leads 108A-C to the heart 105. Cardiac leads 108A-C include a
proximal end that is coupled to IMD 110 and a distal end, coupled by an
electrode or electrodes to one or more portions of a heart 105. The
electrodes typically deliver cardioversion, defibrillation, pacing, or
resynchronization therapy, or combinations thereof to at least one
chamber of the heart 105. The electrodes may be electrically coupled to
sense amplifiers to sense electrical cardiac signals.

[0023] The heart 105 includes a right atrium 100A, a left atrium 100B, a
right ventricle 105A, a left ventricle 105B, and a coronary sinus
extending from right atrium 100A. The atrial lead 108A includes
electrodes (electrical contacts, such as ring electrode 125 and tip
electrode 130) disposed in the right atrium 100A of heart 105 for sensing
signals, or delivering pacing therapy, or both, to the right atrium 100A.

[0024] The ventricular lead 108B includes one or more electrodes, such as
tip electrode 135 and ring electrode 140, for sensing signals, delivering
pacing therapy, or both sensing signals and delivering pacing therapy.
The lead 108B optionally also includes additional electrodes, such as for
delivering atrial cardioversion, atrial defibrillation, ventricular
cardioversion, ventricular defibrillation, or combinations thereof to the
heart 105. Such electrodes typically have larger surface areas than
pacing electrodes in order to handle the larger energies involved in
defibrillation. The lead 108B optionally provides resynchronization
therapy to the heart 105.

[0025] The IMD 110 may include a third cardiac lead 108C attached to the
IMD 110 through the header 155. The third cardiac lead 108C includes ring
electrodes 160, 165 placed in a coronary vein lying epicardially on the
left ventricle (LV) 105B via the coronary vein 120.

[0026] The lead 108B may include a first defibrillation coil electrode 175
located proximal to tip and ring electrodes 135, 140 for placement in a
right ventricle (RV), and a second defibrillation coil electrode 180
located proximal to the first defibrillation coil 175, tip electrode 135,
and ring electrode 140 for placement in the superior vena cava (SVC). In
some examples, high-energy shock therapy is delivered from the first or
RV coil 175 to the second or SVC coil 180. In some examples, the SVC coil
180 is electrically tied to an electrode formed on the
hermetically-sealed IMD can 150. This improves defibrillation by
delivering current from the RV coil 175 more uniformly over the
ventricular myocardium. In some examples, the therapy is delivered from
the RV coil 175 only to the electrode formed on the IMD can 150.

[0027] Other forms of electrodes include meshes and patches which may be
applied to portions of heart 105 or which may be implanted in other areas
of the body to help "steer" electrical currents produced by IMD 110. The
present methods and systems will work in a variety of configurations and
with a variety of electrical contacts or "electrodes." Sensing among
different sets of electrodes often provides directional information
regarding the propagation of cardiac signals and is often referred to as
sensing among different vectors. For example, in a single chamber ICD,
sensing from a right ventricular tip electrode 135 to a right ventricular
ring electrode 140 would be a first vector, and sensing from an RV coil
175 to an electrode on the can 150, or a header 155, would be second
vector. Various electrode configurations may be used.

[0028] The electrode configuration used in the systems and methods
described herein allow for the collection of patient episode data
including electrograms (EGMs) on at least the right ventricular channel,
while multiple channels may be used. The right ventricular EGM signal is
recorded with electrodes implanted in or near a ventricle. For example, a
ventricular channel or vector may include a tip electrode and ring
electrode for the right ventricular channel or ring electrodes for the
left ventricular channel. Another channel, known as the shock channel or
shock vector, may be used. The shock channel is sensed using electrodes
that are also used to delivery high-energy shock therapy. In one example,
the shock channel includes an electrode placed in the RV.

[0029] As will be described with reference to FIG. 13, the IMD has a
processor and memory to store patient episode data to be uploaded by a
communication module. The IMD can overwrite the memory as necessary to
store new patient episode data.

[0030] As will be appreciated by those having skill in the art, over the
life of the patient the leads 108A-108C can experience general wear and
tear, based on its own durability and its environment. Such wear and tear
can cause functionality problems such as inaccurate sensing, inaccurate
treatment, and the like. As such, it is desirable for caregivers to be
able to accurately identify a problematic lead with the information
available, while minimizing "false positive" identification of
problematic leads.

[0031] FIG. 2 depicts a schematic consistent with the technology disclosed
herein. Notification 400 of an issue arising from a suspect lead is
provided to a patient, caregiver, or the like, if rapid sensing is
detected 100, an impedance threshold analysis is positive 200, or an
impedance spike analysis is positive 300. Notification 400 is generally
that a lead condition has been identified through the rapid sensing 100,
impedance threshold analysis 200, or impedance spike analysis 300. The
analyses are generally conducted with a processing module. In a variety
of embodiments, the lead is an implanted lead consistent with an
implanted cardiac rhythm management device depicted in FIG. 1. The
discussion of FIGS. 3-6 below particularly discuss methods consistent
with rapid sensing, while the discussions of FIGS. 7 and 8 particularly
discuss methods consistent with impedance threshold analysis and
impedance spike analysis, respectively.

[0032] In one embodiment, impedance threshold analysis 200 is performed by
a processor in the IMD while impedance spike analysis 300 and rapid
sensing detection 100 is performed by a processor in an external device.
However in another embodiment, analyses 100, 200 and 300 are performed by
the IMD. In another embodiment, analyses 100, 200 and 300 are performed
by the external device.

[0033] Notification 400 can generally be consistent with that known in the
art through a patient and/or caregiver system interface, e-mail, and the
like. Notification 400 will generally be accomplished by one or more
notification modules. Where the analysis is performed in the external
device that prompts the notification 400, notification 400 will generally
be in real time immediately subsequently to the analysis being performed
and include a timestamp of the episode that triggered the notification
400. The system can also be configured to store the notification and
timestamp and analyze data based on the timestamp, and other data
associated with each notification 400, which can be referred to as a
notification record. Notification 400 by the external device will be
described in more detail, below.

[0034] Where an analysis leading to notification is performed by the IMD,
the notification can be part of the episode summary information that is
downloaded to the external device during a communication session.

[0035] FIG. 3 depicts an example high level schematic associated with
rapid sensing detection 100 of FIG. 2. In a communication session between
the IMD and the external device, a summary data record is received 120
for one or more episodes, and an episode of interest determination is
made 140 for each episode in the summary record. If the episode is not of
interest, the analysis ends 150. If the episode is of interest, the
episode is either flagged for upload 160 and then episode data is
received 170, or the episode data is received 170 without first being
flagged 160. Once the episode data record is received by the external
device, a noise determination is made 180, and if there is noise,
notification 400A follows. If there is no noise, the analysis ends 190.

[0036] In a variety of embodiments, episode summary data includes data
that is typically received by a communication module from an IMD, as is
known in the art. Episode summary data can include, for example, the
following data for a particular episode: episode duration, episode zone,
indication that the episode is non-sustained, indication that the episode
is sustained, number of therapy attempts, type of therapy attempt (also
referred to as a therapy indicator), whether episode therapy was
commanded, time of day of the episode, episode number, and type of
episode, as examples. The summary data for a particular episode is then
analyzed to identify whether the episode is an episode of interest 140.

[0037] Typically a communication module associated with an IMD will upload
episode summary data from the IMD in batches of a plurality of episode
summaries based on the episode summary that was last uploaded. Each batch
of episode summary data is included in a summary data record. The episode
summary data that was last uploaded can be identified by, for example, an
episode number. In a variety of embodiments, each episode summary in the
batch of the plurality of episode summaries is analyzed individually to
make a determination whether the episode is an episode of interest 140.
If the episode summary does not identify the episode as an episode of
interest 140, the analysis of that episode summary ends, and the next
episode summary in the batch is considered. If the episode summary does
identify the episode as an episode of interest 140, the episode is
flagged for upload in the future, and the next episode summary data is
analyzed to see if it is an episode of interest 140. Such analysis is
continued until all of the summary data associated with the batch of
episodes have been considered.

[0038] Once the summary data associated with each episode in the batch of
episode summaries have been considered, the episode data associated with
each of the flagged episodes is received 170 in a batch upload from the
IMD. The episode data is then analyzed for noise 180, which is described
in more detail in the discussion associated with FIG. 6. In some
embodiments the episode data for each episode is an electrogram. In a
variety of embodiments the episode data includes marker and summary data
associated with an electrogram. In a variety of embodiments the episode
data is an electrogram as well as episode markers associated with the
electrogram. An example electrogram having associated markers is depicted
in FIG. 5, which is described in more detail, below.

[0039] In example alternate embodiments, episode data for each episode of
interest is received 170 when the episode of interest 140 determination
is made. In such embodiments the episode data is not received 170 in
batches. In some embodiments the noise analysis 180 can likewise be done
on a per-episode basis rather than a batch-basis.

[0040] If noise is not identified 180 in the episode data, then the
analysis ends 190. If noise is identified 180 in the episode data, then
there is notification 400A. The notification 400A can generally convey to
the system user that noise was detected, and can include a timestamp of
the episode that triggered the alert and a summary of the episode. In an
example notification 400A the system alerts the user to check a lead
because a possible right ventricular non-physiological signal was
detected on a particular date at a particular time. In a variety of
embodiments, the data associated with the notification 400A is saved by
the system for future reference. In a variety of embodiments, once
notification 400A of noise associated with a particular episode on a
particular date has been made, no further noise analysis is initiated on
episodes occurring before that particular date. Such analysis may be
considered redundant in some systems.

[0041] FIG. 4 depicts an example schematic associated with identifying an
episode of interest 140 of FIG. 3 based on episode selection criteria
142, 144, 148. The episode selection criteria 142, 144, 148 are applied
to the retrieved episode summary data to determine whether a particular
episode is an episode of interest. Such analysis can be executed by a
processing module, for example. Specifically, the episode summary data
for each episode is examined to identify whether a shock was delivered
during that episode 142, and if a shock is identified, the analysis ends
150. If a shock is not identified, the summary data is examined to
identify anti-tachycardia pacing (ATP). If ATP is identified, the episode
data is identified as of interest 146. If ATP is not identified, the
summary data is examined to identify whether the episode was sustained
148. If the episode was not sustained, the analysis 140 ends 150. If the
episode was sustained, then the episode is identified as of interest 146.

[0042] If episode summary data indicating that a shock was administered is
identified 142 the analysis of the summary data ends 150, and the episode
is not identified as an episode of interest. In a variety of systems,
episodes resulting in the administration of a shock 142 to a patient are
currently afforded a relatively high level of scrutiny based on the high
impact of the shock on the patient and the potentially dangerous
physiological state experienced by the patient. Further, administration
of an improper shock treatment to the patient is typically examined with
haste after the occurrence. As such, notification of noise associated
with episodes leading up to a shocked treatment might often be a
redundant inquiry. In one alternate embodiment, however, episodes where a
shock was administered can be considered an episode of interest.

[0043] If episode summary data indicating that ATP was administered is
identified 144 the episode is determined to be an episode of interest
146, and can be flagged for upload. If ATP is not identified 144 in the
episode summary data, then the episode summary data is analyzed to
identify whether the episode was sustained 148. If the episode summary
data does not identify the episode as sustained, then analysis of the
summary data ends 150, and the episode is not identified as an episode of
interest. If the episode summary data does identify the episode as
sustained, then the episode is identified as an episode of interest 146
and the episode is either flagged for upload or retrieval of the episode
data is initiated from the IMD.

[0044] In a variety of embodiments of the current process, non-sustained
episodes are not considered in the noise analysis 100 to conserve system
resources such as IMD battery life and processing bandwidth. This is
because non-sustained episodes generally occur at a relatively high
frequency when compared with sustained episodes. For purposes of this
application, a "sustained episode" is defined as an episode that meets
minimum time requirements. For example, a "sustained episode" may be
defined in one embodiment as where eight out of ten beats are faster than
a programmed rate threshold and then six out of ten beats remain faster
than the programmed rate threshold, which is maintained for a programmed
length of time.

[0045] Generally the programmed length of time can range from about 1
second to about 60 seconds and the programmed rate threshold can range
from about 160 beats per minute (bpm) to about 200 bpm. In a variety of
embodiments the programmed length of time ranges from about one second to
about 2.5 seconds. In some embodiments the programmed length of time is
one second. In some embodiments the programmed length of time is two
seconds. In some embodiments the programmed length of time is up to sixty
seconds. In some embodiments the programmed rate threshold is 160 bpm. In
some embodiments the programmed rate threshold is 180 bpm. In some
embodiments the programmed rate threshold is 200 bpm.

[0046] As described above with reference to FIG. 3, there can be a batch
of episode summaries that are uploaded for consideration and each episode
summary in the batch is analyzed according to the process steps reflected
in FIG. 4 to determine whether the episode is an episode of interest. In
a variety of embodiments, the system is configured to assess episode
summaries that have not yet been considered. As such, the system can be
configured to store identifying data for the last episode considered,
such as episode number, and assess episode summaries for episodes
occurring subsequent to that last episode.

[0047] Referring back to FIG. 3, retrieval of episode data 170 from the
IMD is initiated for the episodes of interest. In a variety of
embodiments retrieval of episode data 170 is initiated by the
communication module of the external device. In a variety of embodiments,
the episode data is an electrogram. In a variety of embodiments the
episode data is stored in an episode of interest database 189 for access
and analysis. The episode of interest database 189 may be part of memory
of the external device in one embodiment. The episode of interest
database may also be part of a different external memory location, such
as a memory location of a patient management system.

[0048] FIG. 5 depicts a portion of example episode data 500, which is also
referred to herein as an episode data record 500. This particular episode
data 500 has an electrogram portion 510 and an associated marker portion
520. Generally, an IMD consistent with the currently-described technology
determines locations of heart beats within the EGM data 510, resulting in
a group of device-identified beat locations that are device markers 520.

[0049] The EGM portion 510 is generally a graphical representation of the
patient's cardiac activity and the marker portion 520 marks detected
events corresponding to the EGM portion 510. Among other data, the marker
portion 520 can indicate beat-specific data such as the heartbeat zone
522, heartbeat time 524, pacing therapy (not shown), a diverted shock
(not shown), and event detection, as examples. Those having skill in the
art will appreciate the other types of marker data 520 that can be
provided.

[0050] The EGM data 510 and markers 520 are stored in a memory of the IMD.
Once the episodes of interest are determined by a process consistent with
FIGS. 3 and 4, the communication module initiates retrieval of the
episode data record for episode of interest 500 from the IMD. The episode
data 500 is then analyzed in the noise analysis 180 of FIG. 3, which is
described in more detail now with reference to FIG. 6. In one embodiment,
the noise analysis 180 utilizes the marker portion 520 of the episode
data record and does not utilize the EGM portion 510 of the episode data
record.

[0051] By using summary data and episode data currently provided by IMDs
to external devices, it is possible in one embodiment to perform the
noise analysis described here in without any alterations being required
to IMDs or the programming of the IMDs that are coupled to systems
consistent with the technology disclosed herein. Furthermore, changes to
the analysis disclosed herein can be made readily in the processing
module that is external to the IMD, as the situation necessitates.

[0052] FIG. 6 depicts an example schematic associated with noise analysis
180 from FIG. 3. Such analysis can be executed by a processing module,
for example. The episode data can be from the episode of interest
database 189. A number of different analysis steps will be described that
are performed using the episode data. Although these steps have been
presented in a particular order for one embodiment, it is also possible
to change the order of these analysis steps.

[0053] In one step of the analysis, an episode data record associated with
a particular episode is examined for ATP or diverted shock 182. If ATP or
diverted shock 182 is identified, data is disregarded after event
detection marker 184 for a threshold analysis 186. In the threshold
analysis 186 it is determined whether a threshold number of beats are
faster than the noise threshold 186. If the answer to the threshold
analysis 186 is yes, there is notification 400A. If the answer to the
threshold analysis is no, then the analysis ends 190.

[0054] If, on the other hand, ATP or diverted shock 182 is not identified,
the episode data is to determine if the episode data meets the noise
definition of the system. The episode data is analyzed to find a
threshold number of sensed ventricular beats faster than a first fast
interval threshold or noise threshold 183. If such a threshold is not
met, the analysis ends. If the threshold is met, the process looks for
another noisy episode 185 on a different day 187 that also satisfies the
noise definition. If there has not been another noisy episode 185, or the
episode was on the same day 187, the analysis ends 190. If there has been
another noisy episode 185 on a different day 187, notification 400A
follows. The process uses one or more databases 189 that provide data
associated with episodes of interest.

[0055] Identification of ATP 182 can include considering the EGM markers
from the episode data for a marker that indicates ATP. Similarly,
identification of a diverted shock 182 can include considering the EGM
markers from the episode data for a marker that indicates a diverted
shock. In some embodiments, episodes with ATP or a diverted shock are
identified by a marker in the episode data that marks an event detection
resulting in the ATP or diverted shock. An event detection marker or
"detection met" marker indicates that the IMD has decided that a cardiac
event has occurred, according to the IMD's programmed criteria, which
warrants that some type of therapy be provided to the patient. Examples
of therapy that can be provided to the patient include shock or ATP,
among others. In some situations, the criteria for a shock is satisfied,
resulting in an event detection marker and the IMD initiating charging to
deliver a shock, but the IMD decides not to deliver the shock and so
diverts the shock. In some embodiments, these episodes will have a marker
indicating that the shock was diverted. If there are no markers in the
episode data that indicate either ATP or diverted shock, then the episode
is an untreated sustained episode, since the previously-executed
analysis, depicted in FIG. 4, rules out episodes that are non-sustained
or that included a therapeutic shock.

[0056] If the episode data includes a marker for either ATP or diverted
shock 182, a noise analysis is conducted 186 that disregards the episode
data after the event detection 184. In a variety of instances, episode
data collected during or after administered therapy can cause
particularly fast heart beats that may be interpreted by the system as
"noise." As such, it may improve the predictive value of the system to
ignore such data. Additionally, focusing on physiological data that
triggers an event detection to warrant a diverted shock can allow a
system user to improve system analytics.

[0057] The threshold analysis 186 determines whether the episode meets the
noise detection criteria. Particularly, the threshold analysis determines
whether, before the event detection, there are a threshold number of
beats that are each faster than a beat length threshold 186. In at least
one embodiment, the threshold number of beats is four and the beat length
threshold is about 160 milliseconds. Stated differently, the noise
detection criteria are satisfied if, before event detection, the system
identifies at least four beats that are 160 ms or less in length. Those
having skill in the art will recognize other numbers of beats occurring
at alternate beat length thresholds may also be accurate predictors of an
issue with a lead. In a variety of embodiments, the system is configured
to store the outcomes associated with the application of noise detection
criteria to retrieved episode data records.

[0058] The analysis for untreated sustained episodes is similar to the
analysis of episodes with ATP or diverted shock in that the episode data
is considered to identify a threshold number of beats that are faster
than a threshold beat length. If this threshold criteria 183 is met to
indicate that the episode was noisy, notification criteria for untreated
sustained episodes further requires that a second noisy episode be
identified 185. The second noisy episode 185 need be identified as
occurring within the time period since the last notification 400A or
within the last thirty days, whichever is less. In other words, an
episode counter that is configured to count the number of untreated
sustained episodes is restarted at notification 400A, where the
notification 400A is only notification 400A associated with rapid sensing
100. Additionally, the second noisy episode need be on a different day
187 than the first noisy episode. Such notification criteria 185, 187
improve the predictive value of the notification 400A for lead problems
by limiting the likelihood that the sensed noise is caused by the
environment the patient is in.

[0059] As mentioned above, the process uses one or more episode databases
189 that provide data associated with episodes of interest. In a variety
of embodiments, when an episode is identified as meeting the noise
criteria 183, such identification is saved in the episode database 189.
In a variety of embodiments, when an episode is identified as meeting the
noise criteria 183, such identification is counted on a noisy episode
counter which counts noisy episodes within the last 30 days and resets
upon notification 400A.

[0060] FIG. 7 depicts an example schematic associated with impedance
threshold analysis. Such analysis can be executed by a processing module,
for example. In at least one embodiment, such analysis is executed by an
IMD. Pacing/sensing lead impedance Zpace is analyzed to determine
whether it is greater than an upper pacing impedance threshold
Tpace-upper 220 or less than a pacing/sensing lead lower impedance
threshold Tpace-lower 240. If the answer to either analysis 220, 240
is "yes," then notification 400B follows. If the answer to both analysis
is "no," then the analysis ends 500. Similarly, shock lead impedance
Zshock is analyzed to determine whether it is greater than an upper
shock impedance threshold Tshock-upper 260 or less than a lower
shock impedance threshold Tshock-lower 280. If the answer to either
analysis 260, 280 is "yes," then notification 400B follows. If the answer
to both analysis 260, 280 is "no," then the analysis ends 500.

[0061] Generally the Tpace-upper is about 2000Ω and the
Tpace-lower is about 200Ω. Generally Tshock-upper is
about 20Ω, and Tshock-lower is about 125Ω. Those having
skill in the art will appreciate that other values may be used that may
improve predictive value of the notification 400B.

[0062] The notification 400B associated with a lead impedance measurement
can generally convey to the system user of the lead at issue and whether
the impedance measurement was above the threshold value or below the
threshold value. If the resistance measurement is above the threshold
value, the notification 400B can include notifying the system user of
possible lead breakage. If the resistance measurement is below the
threshold value, the notification 400B can include notifying the system
user of possible insulation failure. The notification 300 can also
include a timestamp if the impedance measurement that triggered the alert
and a summary of the event. In a variety of embodiments, the data
associated with the notification 400B is saved by the system for future
reference. In a variety of embodiments, once notification 400B that an
impedance measurement taken on a particular day for a particular lead is
outside the threshold, no further impedance threshold analysis is
initiated for that lead on days occurring before that particular day.
Such analysis may be considered redundant in some systems. In embodiments
where impedance analysis is executed by an IMD, notification 400B can
include communication with a communication module to provide the
notification 400B to an external device. The notification 400B can be
included with a summary data record that is retrieved from the IMD by an
external device.

[0063] Many different impedance threshold analysis methods are known in
the art and in alternate embodiments can be used in combination with the
noise detection analysis and impedance spike analysis described herein.

[0064] FIG. 8 depicts an example schematic associated with an impedance
spike analysis. Such analysis can generally be executed by a processing
module. In one embodiment, the analysis is executed by a processing
module of the external device. The current lead impedance Zcurrent
is received 310 and a 7-day impedance median Zmedian is determined
320. The system identifies a target number of impedance "spikes" relative
to the impedance median Zmedian. Particularly, the threshold
impedance required to qualify as an "impedance spike" can vary based on
the impedance median Zmedian.

[0065] If the 7-day impedance median Zmedian is less than or equal to
a threshold impedance Zthresh, the system looks for three impedance
spikes Zx, y, z that are greater than a first impedance threshold
Z.sub.low-thresh 340. If the 7-day impedance median Zmedian is
greater than the threshold impedance Zthresh, the system looks for
three impedance spikes Zx, y, z that are greater than a second
impedance threshold Z.sub.high-thresh 360. If either analysis 340, 360
identifies three impedance spikes Zx, y, z, then notification 400C
follows. Notification can generally be accomplished by a notification
module. If either analysis 340, 360 does not identify three impedance
spikes Zx, y, z, the analysis ends 380. One or more impedance
databases 390 containing daily impedance data can be used in such an
impedance spike analysis 300.

[0066] Generally the impedance spike analysis takes into account natural
impedance spikes that can occur by virtue of the structure of the IMD
absent relevant lead problems. For example, slight shifts of set screws
used in the IMD can cause a spike in the impedance measurement of a
particular lead. As such, by identifying three spikes in a seven day time
period, the notification 400C of a lead condition has a higher predictive
value that a single spike in the seven day time period. Those having
skill in the art will appreciate that other time periods can be used
other than the seven-day median, such as a five-day median or a nine-day
median, as examples. Similarly, the analysis could also identify more or
less impedance spikes to trigger notification 400C. The number of
impedance spikes required to trigger notification 400C is referred to as
a "spike threshold."In some embodiments, the threshold impedance
Zthresh is about 750Ω. In some embodiments, the first
impedance threshold Z.sub.low-thresh is about 300Ω. In some
embodiments, the second impedance threshold Z.sub.high-thresh is about
750Ω. Those having skill in the art will recognize that other
values can be used for the various impedance thresholds that may improve
predictive value of the analysis.

[0067] In a variety of scenarios the impedance data will be uploaded by
the communication module from the IMD in a batch, depending on the last
uploaded impedance data. In a variety of implementations of the current
technology, receiving Zcurrent will include impedance measurements
up to the last fourteen days, even if it has been more than fourteen days
since the last upload of impedance data. The impedance spike analysis 300
will then apply to each of the seven-day medians within the fourteen-day
period. The analysis of the seven-day median does not include any day on
which there was notification 400C or any day before notification 400C for
a particular lead. In other words, the impedance spike analysis for a
particular lead restarts upon notification 400C, where the notification
400C is only notification 400C associated with impedance spike analysis
300.

[0068] If three impedance spikes are not identified 340, 360 then the
analysis ends 380. If three impedance spikes are identified 340, 360,
then there is notification 400C. The notification 400C can generally
convey to the system user that impedance spikes were detected, and can
include a timestamp of the most recent measurement that triggered the
alert and a summary. In an example notification 400C the system alerts
the user to check a lead due to an abrupt change in the lead impedance in
the past seven days, on a particular date at a particular time. In a
variety of embodiments, the data associated with the notification 400C is
saved by the system for future reference. In a variety of embodiments,
once notification 400C of impedance spikes associated with a particular
lead on a particular date has been made, no further impedance spike
analysis is initiated on measurements occurring before that particular
date. Such analysis may be considered redundant in some systems.

[0069] FIG. 9 depicts a screenshot of an example implementation of the
technology disclosed herein. In a variety of embodiments, such user
interfaces 900 are consistent with the settings for an individual patient
rather than clinic-wide settings so that operational changes for each
patient can take into account particular hardware associated with the
patient.

[0070] In a variety of embodiments, lead check settings 910 have some
non-optional settings 918 and some others are optional settings 916. In
some such embodiments, impedance spike analysis 912 and rapid sensing
analysis 914 are two such optional settings 916. In at least one
embodiment, the impedance spike analysis 912 and the rapid sensing
analysis 914 default to "off". Such a default setting is desirable in
situations where there is a high probability that any patient using such
a system has IMD components that will not substantially benefit from lead
analysis taught herein. For example, it may be determined that leads
having a particularly low probability of failure will likely not benefit
from such lead analyses, especially since the occurrence of a false
positive could lead to unnecessary surgeries to replace leads.

[0071] In other embodiments, it may be desirable that the impedance spike
analysis 912 and the rapid sensing analysis 914 default to "on,"
particularly where such a system is more likely to be used with patient's
having IMD components that would benefit from such analysis, i.e. leads
that have a reasonable risk of failure.

[0072] In a variety of embodiments the interface 900 does not provide the
ability for the user to change the sensitivity of the impedance spike
analysis 912 and the rapid sensing analysis 914.

Description of Hardware Systems

[0073] The above-described method can be implemented on various hardware
systems, such as on a programmer, in a patient management system, or
other computational devices.

[0074] FIG. 10 is a schematic of an exemplary cardiac rhythm management
(CRM) system 1300. The system 1300 can include an IMD 1314 disposed
within a patient 1312. The IMD 1314 can include pacing functionality. The
IMD 1314 can be of various types of devices such as, for example, a
pacemaker, a cardioverter-defibrillator, a cardiac resynchronization
device, a heart rhythm monitoring device, or the like. The IMD 1314
includes one or more leads 1322 disposed in or near the patient's heart
1326.

[0075] The IMD 1314 can be in communication with an external interface
device 1316. In some embodiments, communication between the IMD 1314 and
the external interface device 1316 can be via inductive communication
through a wand 1310 held on the outside of the patient 1312 near the IMD
1314. However, in other embodiments, communication can be carried out via
radio frequency transmission, acoustically, or the like. The particular
device that is configured to retrieve data, including patient data, from
the IMD 1314 is generally referred to as a "communication module."

[0076] The IMD 1314 can include one or more implanted sensors in order to
gather data regarding the patient 1312. For example, the IMD 1314 can
include an activity level sensor, a respiration sensor, a heart sounds
sensor, a blood pressure sensor, an impedance sensor, or other sensors.
The data gathered using the IMD 1314 may be any type of patient data. In
a variety of embodiments, and as described above, the IMD 1314 collects
electrograms from the patient. The patient data can further comprise data
regarding the locations of heart beats within the electrograms. This data
can be collected into groups of device-identified beat locations for each
collected electrogram.

[0077] The IMD 1314 is generally configured to store data over a period of
time, and periodically communicate with the external interface device
1316 in order to transmit some or all of the stored data.

[0078] The external interface device 1316 can be for example, a
programmer, a programmer/recorder/monitor device, a computer, a patient
management system, a personal digital assistant (PDA), or the like. As
used herein, the term programmer refers to a device that programs
implanted devices, records data from implanted devices, and allows
monitoring of the implanted device. Exemplary programmer/recorder/monitor
devices include the Model 3120 Programmer, available from Boston
Scientific Corporation, Natick, Mass. The external interface device 1316
can include a user input device, such as a keyboard 1320 and/or a mouse
1328. The external interface device 1316 can include a video output
channel and video output device, such as a video display 1318 for
displaying video output. The displayed video output can include a user
interface screen. In addition, the video display 1318 can also be
equipped with a touch screen, making it into a user input device as well.

[0079] The external interface device 1316 can display real-time data
and/or stored data graphically, such as in charts or graphs, and
textually through the user interface screen. In addition, the external
interface device 1316 can present textual information to a user along
with several response options. The external interface device 1316 can
also input and store a user's response to a question, and can store a
user's text response in some embodiments.

[0080] In one embodiment, the external interface device 1316, which can
also be referred to as a user interface, is in communication with a
patient management computer system 1332. The communication link between
the user interface 1316 and the patient management computer system 1332
may be via phone lines, the Internet 1330, or any other data connection.
The user interface 1316 can also be used when it is not in communication
with a device, but is only in communication with the patient management
computer system 1332.

[0081] In one embodiment, the external interface device 1316 is capable of
changing the operational parameters of the IMD 1314, and is therefore
referred to as a programmer. Typically, programmers are used to interface
with CRM devices in a clinic or hospital setting. In this context, the
user of the external interface device 1316 is a physician or trained
technician.

[0082] The components that execute the analysis as described herein are
generally referred to as the "processing module." Those having skill in
the art will appreciate that the processing module can include components
of the patient management system 1332, the external interface device
1316, other devices, and combinations thereof Similarly, the components
of the system that generate notifications consistent with the technology
disclosed herein are generally and collectively referred to as the
"notification module," for purposes of this application.

[0083] FIG. 11 is a schematic illustration of a patient management system
consistent with at least one embodiment of the invention. The patient
management system is capable of maintaining an episode database using
computer storage medium. Of note, the episode database may also be
present in an implantable or implanted device as discussed further
herein. A computer storage medium is any technology, including devices
and materials, used to place, keep and retrieve data. Examples of
computer storage medium include random-access memory (RAM), a
network-attached storage device, magnetic storage such as hard disk
drives, optical discs, and a redundant array of independent discs (RAID).

[0084] Patient management system 1400 generally includes one or more
devices 1402, 1404, and 1406, one or more external interface devices
1408, a communication system 1410, one or more remote peripheral devices
1409, and a host 1412. The host 1412 may be a single computing device,
such as a programmer or other patient management device. In some
embodiments, the host 1412 is an external device that communicates
directly with the one or more devices 1402, 1404, and 1406 and does not
require the use of separate external interface devices 1408. In some
embodiments, the host is an external device and receives data, such as
EGM data, from an external database 1480.

[0085] Each component of the patient management system 1400 can
communicate using the communication system 1410. Some components may also
communicate directly with one another. The various components of the
example patient management system 1400 illustrated herein are described
below. The patient management system 1400 may be a single device or
comprise multiple devices. In one embodiment, the patient management
system 1400 is a single external computing device.

[0086] Data-generating devices 1402, 1404, and 1406 can be implantable
devices or external devices that may provide one or more of the following
functions with respect to a patient: (1) sensing, (2) data analysis, and
(3) therapy. For example, in one embodiment, devices 1402, 1404, and 1406
are either implanted or external devices used to measure a variety of
physiological, subjective, and environmental conditions of a patient
using electrical, mechanical, and/or chemical means. In a variety of
embodiments, at least one of the devices 1402, 1404, 1406 is an IMD.

[0087] The devices 1402, 1404, and 1406 can be configured to automatically
gather data or can require manual intervention by the patient or another
person. The devices 1402, 1404, and 1406 can be configured to store data
related to the physiological and/or subjective measurements and/or
transmit the data to the communication system 1410 using a variety of
methods, described in detail below. Although three devices 1402, 1404,
and 1406 are illustrated in the example embodiment shown, many more
devices can be coupled to the patient management system. In one
embodiment, each of the devices 1402, 1404 and 1406 is serving a
different patient. In one embodiment, two or more devices are serving a
single patient.

[0088] The devices 1402, 1404, and 1406 can be configured to analyze the
measured data and act upon the analyzed data. For example, the devices
1402, 1404, and 1406 can be configured to modify therapy or provide an
alarm based on the analysis of the data.

[0089] In one embodiment, devices 1402, 1404, and 1406 provide therapy.
Therapy can be provided automatically or in response to an external
communication. Devices 1402, 1404, and 1406 are programmable in that the
characteristics of their sensing, therapy (e.g., duration and interval),
or communication can be altered by communication between the devices
1402, 1404, and 1406 and other components of the patient management
system 1400. Devices 1402, 1404, and 1406 can also perform self-checks or
be interrogated by the communication system 1410 to verify that the
devices are functioning properly. Examples of different embodiments of
the devices 1402, 1404, and 1406 are provided herein.

[0091] Devices 1402, 1404, and 1406 can also be external devices, or
devices that are not implanted in the human body, that are used to
measure physiological data (e.g., a thermometer, sphygmomanometer, or
external devices used to measure blood characteristics, body weight,
physical strength, mental acuity, diet, heart characteristics, and
relative geographic position).

[0092] The patient management system 1400 may also include one or more
remote peripheral devices 1409 (e.g., cellular telephones, pagers, PDA
devices, facsimiles, remote computers, printers, video and/or audio
devices) that use wired or wireless technologies to communicate with the
communication system 1410 and/or the host 1412.

[0093] The database module 1414 comprises memory for storing patient data.
The patient data can include electrogram data, which comprises groups of
device-identified beat locations for the electrogram data. This data may
be received from a patient device, such as an implantable medical device,
or it may be retrieved from another database 1480. The example database
module 1414 includes a patient database 1440 and an episode database
1442, which are described further below. The patient database 1440
includes patient specific data, including data acquired by the devices
1402, 1404, and 1406, such as electrogram data, as well as a patient's
medical records and historical information. The episode database 1442 has
episode data regarding a plurality of different episodes generated from
those of devices 1402, 1404, and 1406 that provide episode data. The
episode database 1442 may also store data analyzed by the analysis module
1416.

[0094] Information can also be provided from an external source, such as
external database 1480. For example, the external database 1480 could
include external medical records maintained by a third party, such as
drug prescription records maintained by a pharmacy, providing information
regarding the type of drugs that have been prescribed for a patient or,
in another example, authorization data from patient groups that have
authorized users to view arrhythmia episode data. The external database
1480 may also store patient data that was previously acquired by an
implantable or external medical device. One example of stored patient
data on an external database 1480 is electrogram data.

[0095] The example analysis module 1416 includes a patient analysis module
1450 and a device analysis module 1452. Patient analysis module 1450 may
utilize information collected by the patient management system 1400, as
well as information for other relevant sources, to analyze data related
to a patient and provide timely and predictive assessments of the
patient's well-being. Device analysis module 1452 analyzes data from the
devices 1402, 1404, and 1406 and external interface devices 1408 to
predict and determine device issues or failures. For example, the device
analysis module 1452 may analyze electrogram data to determine locations
of heart beats on one or more channels using the multi-pass methods
described above. The device analysis module 1452 can further compare
device-identified beats and beat locations to beats and beat locations
determined using the multi-pass method. The device analysis module 1452
can then perform comparisons to find the presence of noise, oversensing,
and undersensing by the device, as described above.

[0096] The analysis module 1416 further includes an adjudication processor
1458, and episode processor 1460 and an overwrite processor 1462. In one
embodiment, the adjudication processor is operatively connected to at
least the episode database 1442 and is configured to receive as input
episode data regarding one of the different episodes.

[0097] The episode processor 1460 performs processing of the adjudication
database such as in order to provide reports, patient alerts, or
programming recommendations. The overwrite processor 1462 can analyze
data provided from the episode database 1442, and other portions of the
patient management system 1400 to determine what particular portion of
episode data for one of the episodes from the episode database should be
displayed to a user. Overwrite processor 1462 can, through the delivery
module 1418 described below, provide the means for graphically displaying
a portion of data selected from arrhythmia episode data related to an
episode of a patient, such as data generated by a data-generating device
and stored in the episode database.

[0098] Overwrite processor 1462 also requests from a user any changes in
the characterization data determined by the adjudication processor, and
can articulate the request for user input characterizing an episode. The
request may be a direct question to a user, a series of choices provided
to the user, or simply a blank space on the user interface configured to
accommodate the user input. The overwrite processor 1462 may also store
the overwrite history for individual users.

[0099] One or more portions of the analysis module 1416, such as the
adjudication processor 1458 and episode processor 1460 may be located
remotely from other parts of the patient management system 1400. A
microprocessor of a data-generating device may also serve as an
adjudication processor in some embodiments.

[0100] Delivery module 1418 coordinates the delivery of reports, patient
alerts or programming recommendations based on the analysis performed by
the host 1412. For example, based on the data collected from the devices
and analyzed by the host 1412, the delivery module 1418 can deliver
information to the caregiver, user, or to the patient using, for example,
a display provided on the external interface device 1408. A user
interface device 1490 that is independent of a data-generating device may
also be used to deliver information. The external interface device 1408
and user interface device 1490 are also configured, according to multiple
embodiments, to display a report, alert, or programming recommendation,
receive overwrite information from a user, and receive other data from
the user. Displayed data, as described above, can be determined by the
episode processor 1460, overwrite processor 1462 and delivery module
1418.

[0101] External interface devices 1408 to display information, such as
programmer/recorder/monitors, can include components common to many
computing devices. User interface devices 1490 to display and received
information from users can also include components common to many
computing devices. Referring now to FIG. 12, a diagram of various
components is shown in accordance with some embodiments of the invention.
However, it is not required that an external interface device have all of
the components illustrated in FIG. 12.

[0102] In one embodiment, the external interface device includes a central
processing unit (CPU) 1505 or processor, which may include a conventional
microprocessor, random access memory (RAM) 1510 for temporary storage of
information, and read only memory (ROM) 1515 for permanent storage of
information. A memory controller 1520 is provided for controlling system
RAM 1510. A bus controller 1525 is provided for controlling data bus
1530, and an interrupt controller 1535 is used for receiving and
processing various interrupt signals from the other system components.

[0103] Mass storage can be provided by diskette drive 1541, which is
connected to bus 1530 by controller 1540, CD-ROM drive 1546, which is
connected to bus 1530 by controller 1545, and hard disk drive 1551, which
is connected to bus 1530 by controller 1550. User input to the programmer
system may be provided by a number of devices. For example, a keyboard
and mouse can connected to bus 1530 by keyboard and mouse controller
1555. DMA controller 1560 is provided for performing direct memory access
to system RAM 1510. A visual display is generated by a video controller
1565 or video output, which controls video display 1570. The external
system can also include a telemetry interface 1590 or telemetry circuit
which allows the external system to interface and exchange data with an
implantable medical device. It will be appreciated that some embodiments
may lack various elements illustrated in FIG. 12.

[0104] Referring now to FIG. 13, some components of an exemplary IMD 1600
are schematically illustrated. The IMD 1600 can include a controller made
up of a microprocessor 1610 communicating with a memory 1612, where the
memory 1612 may comprise a ROM (read-only memory) for program storage and
a RAM (random-access memory) for data storage. The controller could be
implemented by other types of logic circuitry (e.g., discrete components
or programmable logic arrays) using a state machine type of design, but a
microprocessor-based system is preferable. The controller is capable of
operating the IMD 1600 in a number of programmed modes where a programmed
mode defines how pacing pulses are output in response to sensed events
and expiration of time intervals.

[0105] A telemetry interface 1680 is provided for communicating with an
external programmer 1675. The external programmer is a computerized
device with a controller 1677 that can interrogate the IMD 1600 and
receive stored data as well as adjust the operating parameters of the
pacemaker.

[0106] The IMD 1600 has an atrial sensing/pacing channel comprising ring
electrode 1633A tip electrode 1633B sense amplifier 1631, pulse generator
1632, and an atrial channel interface 1630 which communicates
bi-directionally with a port of microprocessor 1610. The device also has
two ventricular sensing/pacing channels that similarly include ring
electrodes 1643A and 1653A tip electrodes 1643B and 1653B sense
amplifiers 1641 and 1651, pulse generators 1642 and 1652, and ventricular
channel interfaces 1640 and 1650. For each channel, the electrodes are
connected to the IMD 1600 by a lead and used for both sensing and pacing.
A MOS switching network 1670 controlled by the microprocessor is used to
switch the electrodes from the input of a sense amplifier to the output
of a pulse generator. A shock channel is also provided comprising a shock
pulse generator 1690 and shock electrodes 1691A and 1691B that enables
the device to deliver a defibrillation shock to the heart when
fibrillation or other tachyarrhythmia is detected. The IMD 1600 also has
an evoked response sensing channel that comprises an evoked response
channel interface 1620 and a sense amplifier 1621 that has its
differential inputs connected to a unipolar electrode 1623 and to the
device housing or can 1660 through the switching network 1670. The evoked
response sensing channel may be used to verify that a pacing pulse has
achieved capture of the heart in a conventional manner or, as explained
below, used to record an evoked response electrogram.

[0107] The channel interfaces include analog-to-digital converters for
digitizing sensing signal inputs from the sensing amplifiers, registers
that can be written to for adjusting the gain and threshold values of the
sensing amplifiers, and, in the case of the ventricular and atrial
channel interfaces, registers for controlling the output of pacing pulses
and/or adjusting the pacing pulse energy by changing the pulse amplitude
or pulse width. The microprocessor 1610 controls the overall operation of
the device in accordance with programmed instructions stored in memory.
The sensing circuitry of the IMD 1600 generates atrial and ventricular
sense signals when voltages sensed by the electrodes exceed a specified
threshold. The controller then interprets sense signals from the sensing
channels and controls the delivery of paces in accordance with a
programmed pacing mode. The sensed signals from any of the sensing
channels of the IMD 1600 in FIG. 13 can be digitized and recorded by the
controller to constitute an electrogram that can either be transmitted
via the telemetry link 1680 to the external programmer 1675 or stored for
later transmission. The patient's cardiac activity may thus be observed
in real-time or over a selected historical period.

[0108] The above-described method can be regularly initiated to analyze
the implanted leads. Gathered data may be used as input for other device
functionality, such as arrhythmia adjudication.

[0109] It should be noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the" include plural
referents unless the content clearly dictates otherwise. It should also
be noted that the term "or" is generally employed in its sense including
"and/or" unless the content clearly dictates otherwise.

[0110] It should also be noted that, as used in this specification and the
appended claims, the phrase "configured" describes a system, apparatus,
or other structure that is constructed or configured to perform a
particular task or adopt a particular configuration. The phrase
"configured" can be used interchangeably with other similar phrases such
as "arranged", "arranged and configured", "constructed and arranged",
"constructed", "manufactured and arranged", and the like.

[0111] One of ordinary skill in the art will understand that the modules,
circuitry, and methods shown and described herein with regard to various
embodiments of the invention can be implemented using software, hardware,
and combinations of software and hardware. As such, the illustrated
and/or described modules and circuitry are intended to encompass software
implementations, hardware implementations, and software and hardware
implementations.

[0112] All publications and patent applications in this specification are
indicative of the level of ordinary skill in the art to which this
invention pertains. All publications and patent applications are herein
incorporated by reference to the same extent as if each individual
publication or patent application was specifically and individually
indicated by reference.

[0113] This application is intended to cover adaptations or variations of
the present subject matter. It is to be understood that the above
description is intended to be illustrative, and not restrictive. The
scope of the present subject matter should be determined with reference
to the appended claims, along with the full scope of equivalents to which
such claims are entitled.